Re: [Elecraft] Solar Charge Controllers (was Field Day)

[Jim Brown]

On Wed,6/8/2016 8:42 PM, Jack Brindle wrote:

Thee is an issue with the cheaper solar controllers - they tend to place the 
switching transistor in the ground leg, making connections difficult. For 
example the Sunforce controller that Jim mentions uses an N-channel FET as its 
pass transistor, in the ground lead. If you then connect the radio or other 
load to the battery while it is being charged, you can end up with a floating 
ground. One local solar expert discovered that his setup of this kind caused 
massive current flow on the shield connection of a USB cable - it was 
essentially carrying all the ground current!


Thanks for the alert, Jack. However -- the controller I referenced is a 
low power product, specifically designed for a single panel charging a 
battery. Such panels are rarely connected to a ground except via the 
return side of the pair feeding the battery through the charge regulator.


Also, if a USB cable is the only connection between equipment in a 
system, that system lacks proper bonding.


Abuse of the return conductor is not limited to devices like these. The 
very popular Watts Up inline volt-ammeter meters in the return lead, 
which can lead to very wrong answers when used to measure current within 
a station, for exactly the reasons Jack notes -- DC return current 
divides between the intentional path (the return wire) and all of the 
other return connections between equipment in a station, and bonding 
conductors.


The Hamsource EZmeter ($80) and the West Mountain Radio PWRcheck ($180), 
both sold by DX Engineering, measure current in the positive conductor. 
I found the EZmeter at Pacificon last fall and quickly added it to my 
collection of test gear.


73, Jim K9YC

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Re: [Elecraft] Solar Charge Controllers (was Field Day)

[Jack Brindle]

Thee is an issue with the cheaper solar controllers - they tend to place the 
switching transistor in the ground leg, making connections difficult. For 
example the Sunforce controller that Jim mentions uses an N-channel FET as its 
pass transistor, in the ground lead. If you then connect the radio or other 
load to the battery while it is being charged, you can end up with a floating 
ground. One local solar expert discovered that his setup of this kind caused 
massive current flow on the shield connection of a USB cable - it was 
essentially carrying all the ground current!

The better controllers use P-channel FETs in the positive leg of the charger, 
as shown in Mike Bryce (WB8VGE)’s design in the ARRL publication “Emergency 
Power For Radio Communications” and also in the CirKits design that Bill 
mentions. I have a pair of each of these and will be using them this Field Day 
to keep a pair of Marine deep-cycle batteries charged from a 100 watt solar 
array and also a 45 watt backup array. I like the WB8VGE design better, but it 
won’t handle the 100 watt array without modification, which caused me to pick 
up the CCS3 boards. Unfortunately the WB8VGE kits appear to no longer be 
available, but the CirKits boards (also designed and sold by a ham, forgot his 
call) are very much available and a fun build.

- Jack, W6FB

P.S. Listen for both Bill, myself and many others from the WVARA operation at 
Mora Hill, CA using the call K6EI in FD. It is an all-K3/QRP operation with 
outstanding antennas in a location you have to see to believe. And, if you are 
in the area and searching for a place to play, look us up!


> On Jun 8, 2016, at 10:36 AM, Jim Brown  wrote:
> 
> Yes on all counts. This unit would be described as a simple hysteresis 
> controller -- it doesn't pulse the charge current, it simply turns charging 
> on if the battery voltage is less than full charge, turns charging off when 
> that voltage is reached, and turns charging back on when battery voltage has 
> dropped some pre-set amount. Chargers like this are, by their nature, free of 
> RFI, because there's no square wave to generate RF trash. Several years ago, 
> a local ham pointed me to this product, which does the same thing, but is 
> rated for a lot less current.
> 
> https://www.amazon.com/Sunforce-7-Amp-Charge-Controller/dp/B0006JO0XI/ref=sr_1_1?srs=2601531011&ie=UTF8&qid=1465406526&sr=8-1&keywords=solar+charge+controller
> 
> The more efficient charge controllers of which Bill speaks are MPPT 
> controllers; they have a DC-DC converter that converts the relatively high 
> panel voltage at low current to lower voltage at the higher current that the 
> battery can accept. This allows a large battery to accept more charge in a 
> shorter period of time. By their nature, they use square waves, so they can 
> be noisy, and most MPPT charge controllers ARE noisy. The Genesun MPPT 
> controllers create very little RF noise, and won't be heard in most 
> installations. My solar panels are next to my 160M antenna, so I need a choke 
> on panel side of the controller to prevent noise pickup on that antenna. 
> That's a pretty extreme condition. :) So I'd call the Genasun controllers RF 
> quiet.
> 
> 73, Jim K9YC
> 
> On Tue,6/7/2016 6:12 PM, Bill Frantz wrote:
>> I have been using a solar charge controller from CIrKits 
>> . The kit comes in a 20A version and there are 
>> modification instructions for 40A, 60A, and 80A. I have the 20A version and 
>> have noticed no RFI in my suburban QTH. The higher current modifications 
>> change some of the circuit resistors to keep the RFI low, so low RFI was one 
>> of the design goals.
>> 
>> This controller feeds full panel current to the battery until the voltage 
>> reaches the float voltage and then floats the battery at that voltage. This 
>> techniqueis a good for lead-acid batteries but is probably not appropriate 
>> for lithium family chemistries.
>> 
>> It is also not the most efficient way to charge a lead-acid battery. Higher 
>> efficiency can be achieved by charging at a slightly higher voltage and only 
>> reducing the voltage to the float voltage when the charge current becomes 
>> low. With my 7.5A rated panels, I can recover the batteries charge in a day 
>> after spending a weekend contesting at 100W, so the additional efficiency is 
>> not a major concern. The charge system also works well on field day at QRP 
>> power levels.
> 
> 
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[Elecraft] Solar Charge Controllers (was Field Day)

[Jim Brown]

Yes on all counts. This unit would be described as a simple hysteresis 
controller -- it doesn't pulse the charge current, it simply turns 
charging on if the battery voltage is less than full charge, turns 
charging off when that voltage is reached, and turns charging back on 
when battery voltage has dropped some pre-set amount. Chargers like this 
are, by their nature, free of RFI, because there's no square wave to 
generate RF trash. Several years ago, a local ham pointed me to this 
product, which does the same thing, but is rated for a lot less current.


https://www.amazon.com/Sunforce-7-Amp-Charge-Controller/dp/B0006JO0XI/ref=sr_1_1?srs=2601531011&ie=UTF8&qid=1465406526&sr=8-1&keywords=solar+charge+controller

The more efficient charge controllers of which Bill speaks are MPPT 
controllers; they have a DC-DC converter that converts the relatively 
high panel voltage at low current to lower voltage at the higher current 
that the battery can accept. This allows a large battery to accept more 
charge in a shorter period of time. By their nature, they use square 
waves, so they can be noisy, and most MPPT charge controllers ARE noisy. 
The Genesun MPPT controllers create very little RF noise, and won't be 
heard in most installations. My solar panels are next to my 160M 
antenna, so I need a choke on panel side of the controller to prevent 
noise pickup on that antenna. That's a pretty extreme condition. :) So 
I'd call the Genasun controllers RF quiet.


73, Jim K9YC

 On Tue,6/7/2016 6:12 PM, Bill Frantz wrote:
I have been using a solar charge controller from CIrKits 
. The kit comes in a 20A version and 
there are modification instructions for 40A, 60A, and 80A. I have the 
20A version and have noticed no RFI in my suburban QTH. The higher 
current modifications change some of the circuit resistors to keep the 
RFI low, so low RFI was one of the design goals.


This controller feeds full panel current to the battery until the 
voltage reaches the float voltage and then floats the battery at that 
voltage. This techniqueis a good for lead-acid batteries but is 
probably not appropriate for lithium family chemistries.


It is also not the most efficient way to charge a lead-acid battery. 
Higher efficiency can be achieved by charging at a slightly higher 
voltage and only reducing the voltage to the float voltage when the 
charge current becomes low. With my 7.5A rated panels, I can recover 
the batteries charge in a day after spending a weekend contesting at 
100W, so the additional efficiency is not a major concern. The charge 
system also works well on field day at QRP power levels.



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